The present invention relates in general to a gas compressor for, for example, a refrigerating apparatus and an air conditioning system, and more particularly to a scroll compressor in which air or other gas is compressed to increase its pressure. Generally, the scroll compressor has an orbiting scroll member which includes an end plate and a spiral member or a wrap extending substantially in an involute curve and attached to one surface of the end plate in an upstanding position, and a fixed scroll member which is similar to the orbiting scroll member and is arranged in a juxtaposed relation thereto with the wraps of both members being fitted closely together. The orbiting scroll member is moved in an orbiting motion while rotation about its own axis is inhibited by an Oldham's ring disposed between, for example, the orbiting scroll member and a main frame or a housing. The orbiting movement of the orbiting scroll member reduces a sealed space or a fluid pocket defined by the two scroll members and thus compresses a gas therein to increase its pressure.
The structure and operational mechanism of the scroll compressor described above are old and have advantages when compared to an old piston-type compressor but, on the other hand, have disadvantages and problems of unsatisfactory sealing of a fluid pocket of the wraps, wear of the wraps, and pumping in and out of the used fluid. Attempts have been made to overcome these disadvantages as disclosed in U.S. Pat. Nos. 3884599 and 3924977. However, these attempts have not yet satisfactorily solved other problems related to damage during liquid compression and an increase of a pushing force of the two wraps when a rotational speed of an electric motor is changed.
In a scroll compressor, fluid pockets are formed between connected portions of the two cooperative wraps and the connected portions are moved toward the center along the surface of the wraps by a relative movement of the two scroll members. Under this movement, the fluid pocket moves toward the center to compress a fluid and, accordingly, a sealing of the moving connected portions must be fully insured. In order to try to obtain a desired sealing force, an attempt may be made to increase the connecting force of the wraps which, however, produces undesired wear of the wraps. Thus, the connecting force of the wraps must be determined to produce a suitable sealing force. However, the connecting force of the wraps is not always maintained constant when the orbiting scroll member is driven at a fixed crank radius, due to a production measurement error of the wraps and, reducing such a measurement error during production will undoubtedly be difficult.
Furthermore, if liquid compression occurs that is produced when a liquid refrigerant is introduced into a compression chamber, and one of the scroll members for the fluid compression is undergoing orbiting movement, there is a disadvantage in that the compressor body is vibrated by the orbiting movement of the scroll member. And, in particular, when a rotational speed of an electric motor for the orbiting movement is changed by, for example, inverter driving, a centrifugal force becomes increased by the orbiting scroll member undergoing orbiting movement and the connecting force of the wraps of the two scroll members is tremendously increased resulting in problematic wear of the wraps. These problems are not fully solved by the above-described U.S. Patents.